Modern wind turbines are commonly used to supply electricity into the electrical grid. Wind turbines of this kind generally comprise a rotor with a rotor hub and a plurality of blades. The rotor with the blades is set into rotation under the influence of the wind on the blades. The rotation of the rotor shaft either directly drives the generator rotor (“directly driven”) or through the use of a gearbox. In the turbines using a gearbox, the rotation of a slow speed shaft (which commonly is the rotor shaft), is transformed through suitable gearing to rotation of a high speed shaft, which drives the generator.
EP 1 617 075 discloses a system and method for temporarily supporting a rotor shaft when a gearbox is being substituted. The rotor hub is connected to the shaft. A support structure (yoke) for the rotor shaft ensures that the rotor hub and blades do not need to be removed from the rotor shaft to be able to substitute the gearbox without damaging the main rotor bearings. The yoke comprises adjustment means for adjusting its height.
It is important that the gearbox and/or generator are properly aligned with the wind turbine rotor. Misalignment can lead to an increase in vibrations, cyclical loads and material stresses. Proper alignment however can be hard to achieve. Components such as the rotor, the gearbox and the generator are usually installed using cranes or other hoisting apparatus, which inherently have a certain imprecision during installation. The weight of the components is also substantial and achieving a good alignment of the various components can be a difficult, and laborious and thus expensive task.
Furthermore, it can happen that during operation of a wind turbine, components that were properly aligned when installed become slightly misaligned. Creep is the most common cause for this kind of misalignment. If the misalignment goes unnoticed, the higher loads and vibrations may lead to a shorter life-time of key components. If the misalignment is noticed, the turbine normally is stopped and components have to be repositioned. (Lifting and) repositioning of some components may require additional tools. The interruption of the operation and the subsequent servicing can represent an important cost.
There thus exists a need for facilitating the alignment of wind turbine components during installation. There also exists a need for a method and system for remedying misalignment occurring after installation. Additionally, a need exists to securely monitor the alignment of the wind turbine components.